Flow sensor for sensor network in controlled environment agriculture

ABSTRACT

Systems, methods and computer-readable media are provided for fluid flow measurement in a controlled agricultural environment. A digital flow sensor comprises a flow sensor element including a first digital thermometer for providing a first output and a heating element thermally coupled to the first digital thermometer. The flow sensor may also include a second digital thermometer for providing a second output, and logic for providing a flow measurement based at least in part upon the first and second outputs. A flow sensor network may include multiple digital flow sensors, where data lines of the flow sensors are all coupled to the same network bus for communicating data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication No. 63/061,439, filed 5 Aug. 2021, and incorporated byreference in its entirety herein.

BACKGROUND Field of the Disclosure

The disclosure relates generally to the field of agriculture, and inparticular to a flow sensor adapted for use in a sensor network in acontrolled agricultural environment.

Description of the Related Art

The subject matter discussed in the background section should not beassumed to be prior art merely as a result of its mention in thebackground section. Similarly, a problem mentioned in the backgroundsection or associated with the subject matter of the background sectionshould not be assumed to have been previously recognized in the priorart. The subject matter in the background section merely representsdifferent approaches, which in and of themselves may also correspond toimplementations of the claimed technology.

During the twentieth century, agriculture slowly began to evolve from aconservative industry to a fast-moving high-tech industry in order tokeep up with world food shortages, climate change, and societal changes.Farming began to move away from manually-implemented agriculturaltechniques toward computer-implemented technologies. Conventionally,farmers only have one growing season to produce the crops that woulddetermine their revenue and food production for the entire year.However, this is changing. With indoor growing as an option, and withbetter access to data processing technologies and other advancedtechniques, the science of agriculture has become more agile. It isadapting and learning as new data is collected and insights aregenerated.

Advancements in technology are making it feasible to control the effectsof nature with the advent of “controlled indoor agriculture,” otherwiseknown as “controlled environment agriculture” or “CEA.” Similarly, as toterminology this disclosure concerns embodiments of a controlledagricultural environment (“CAE”), such as an indoor farm. Improvedefficiencies in space utilization and lighting, a better understandingof hydroponics, aeroponics, and crop cycles, and advancements inenvironmental control systems have allowed humans to better recreateenvironments conducive for agriculture crop growth with the goals ofgreater harvest weight yield per square foot, better nutrition and lowercost.

US Patent Publication Nos. 2018/0014485 and 2018/0014486, both assignedto the assignee of the present disclosure and incorporated by referencein their entirety herein, describe environmentally controlled verticalfarming systems. The vertical farming structure (e.g., a verticalcolumn) may be moved about an automated conveyance system in an open orclosed-loop fashion, exposed to precision-controlled lighting, airflowand humidity, with ideal nutritional support.

For an indoor farm, ideally optimum growth conditions are determined forthe plants and the HVAC system is adjusted to obtain those optimumgrowth conditions. Of course, for a particular crop the optimum growthconditions are usually those desired for an indoor farm. However, anumber of factors may hamper implementation of desired conditions,including fully or partially clogged pipes and irrigation lines withinthe indoor farm itself or within environmental conditioning equipmentfor the indoor farm.

The CAE may include hundreds or thousands of nutrient water nozzles andother fluid conduits, all of which are subject to flow blockage.Blockages can cause plant rot and death. Conventional flow sensors arenot easily scalable because they require equipment that is mechanicallyor electrically complex at the site measurement. Capacitive sensorsmeasure whether a pipe is full or empty, but do not detect a clog.Paddle wheel sensors are prone to breakdown because of moving parts.Ultrasonic sensors are complex (and thus expensive) due to thecomplexity of the components (e.g., transducers, signal processing)required. Moreover, they must be precisely manufactured and calibratedto ensure they resonate at the correct frequency.

A constant temperature anemometer (“CTA”) determines flow based on thecooling effect of flow on a heated body, such as a wire placed normal tothe flow. The convective heat transfer from the wire is a function ofthe velocity of the flow. The wire is connected to one arm of aWheatstone bridge and heated by the electric current flowing through thebridge. A servo amplifier controls the current so that the resistance inthe sensor bridge arm—and thus the temperature—is kept constant,independent of the cooling imposed by the fluid. The bridge voltagerepresents the heat transfer and is thus a direct measure of thevelocity. The bridge voltage is low-pass filtered and converted to adigital signal via an analog-to-digital converter. However, theconventional CTA suffers from disadvantages, including that each CTA isconceived as a stand-alone unit.

Moreover, the CTA requires that current flows through the heatingelement (e.g., wire), and that the heating element be in contact withthe sensed fluid. This arrangement limits the CTA to designs in whichthe heating element is compatible with the sensed fluid (e.g., so thatthe element will not oxidize or shed debris into the fluid).

There is a need for a simple and easily scalable flow sensor thatovercomes the disadvantages of conventional approaches and that can beincorporated into a network of such flow sensors within a CAE.

SUMMARY OF THE DISCLOSURE

The disclosure describes systems, methods and computer-readable mediastoring instructions for flow sensing in a controlled agriculturalenvironment (CAE). According to embodiments of the disclosure, a digitalflow sensor comprises a flow sensor element including a first digitalthermometer for providing a first output and a heating element thermallycoupled to the first digital thermometer. The flow sensor may furthercomprise a second digital thermometer for providing a second output, toform a differential flow sensor.

Logic may provide a flow measurement based at least in part upon thefirst and second outputs. The logic may provide the flow measurement inresponse to the flow sensor element and the second digital thermometerbeing thermally coupled to a flowing fluid, with the flow sensor elementdisposed downstream of the second digital thermometer.

The flow sensor may further comprise a thermally conductive elementthermally coupled to the flow sensor element, to form a flow sensorassembly. The thermally conductive element may be disposed in a wall ofa fluid channel to enable thermal coupling to a fluid when the fluidflows in the channel. The thermally conductive element or the heatingelement or both may have a thermal conductivity of at least 5 W/mK.

The flow sensor element may include a single-wire bus for communicatingdata and commands, and for receiving power. According to embodiments ofthe disclosure, the heating element is not part of a Wheatstone bridgecircuit. According to embodiments of the disclosure, the logic does notperform analog-to-digital conversion on voltage of a Wheatstone bridgethat includes the heating element. According to embodiments of thedisclosure, the first digital thermometer includes an integratedtemperature sensor component that is not thermally coupled to a heatingelement within the first digital thermometer. According to embodimentsof the disclosure, the first digital thermometer includes no movingparts.

According to embodiments of the disclosure, a flow sensor networkcomprises multiple digital flow sensors, wherein data lines of thedigital flow sensors in the network are all coupled to the same bus forcommunicating data. According to embodiments of the disclosure, commandsare also communicated over the network bus. According to embodiments ofthe disclosure, the network bus is a single-wire bus. According toembodiments of the disclosure, the heating elements of the digital flowsensors in the network are coupled to the same current source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating an example of acontrolled environment agriculture system.

FIG. 2 is a perspective view of an example of a controlled environmentagriculture system.

FIGS. 3A and 3B are perspective views of an example grow tower.

FIG. 4A is a top view of an example grow tower; FIG. 4B is aperspective, top view of an example grow tower; FIG. 4C is an elevationview of a section of an example grow tower; and FIG. 4D is a sectional,elevation view of a portion of an example grow tower.

FIG. 5A is a perspective view of a portion of an example grow line.

FIG. 5B is a perspective view of an example tower hook.

FIG. 6 is an exploded, perspective view of a portion of an example growline and reciprocating cam mechanism.

FIG. 7A is a sequence diagram illustrating operation of an examplereciprocating cam mechanism.

FIG. 7B illustrates an alternative cam channel including an expansionjoint.

FIG. 8 is a profile view of an example grow line and irrigation supplyline.

FIG. 9 is a side view of an example tower hook and integrated funnelstructure.

FIG. 10 is a profile view of an example grow line.

FIG. 11A is perspective view of an example tower hook and integratedfunnel structure; FIG. 11B is a section view of an example tower hookand integrated funnel structure; and FIG. 11C is a top view of anexample tower hook and integrated funnel structure.

FIG. 12 is an elevation view of an example carriage assembly.

FIG. 13 is a functional block diagram illustrating an irrigation loopaccording to embodiments of the disclosure.

FIG. 14A illustrates an example gutter according to embodiments of thedisclosure; FIG. 14B is a side elevation view of a collector endstructure of the gutter; FIG. 14C is a perspective view of the collectorend structure; FIG. 14D is a perspective view of a gutter section; andFIG. 14E is a side elevation view of the gutter section.

FIG. 15A is a perspective view of an example irrigation skid; and FIG.15B is a side elevation view of the irrigation skid.

FIG. 16A is a sectional view of an irrigation line including a nozzle;FIG. 16B is a perspective view of an irrigation line and nozzle; FIG.16C is a sectional view of a nozzle disposed within an aperture of theirrigation line; and FIG. 16D is a side view of an alternative nozzle.

FIG. 17A is a sectional view of an irrigation line including a nozzlewith an air-bleed element; FIG. 17B is a perspective view of anirrigation line and nozzle with an air-bleed element; and FIG. 17C is asectional view of a nozzle with an air-bleed element disposed within anaperture of the irrigation line.

FIG. 18 is a schematic diagram of an irrigation line according toembodiments of the disclosure.

FIG. 19 illustrates a grow space and an environmental conditioningsystem for conditioning air and fluid in the grow space, according toembodiments of the disclosure.

FIG. 20 illustrates an example of a computer system that may be used toexecute instructions stored in a non-transitory computer readable medium(e.g., memory) in accordance with embodiments of the disclosure.

FIG. 21 illustrates an enhanced HVAC system including an economizersubsystem and an air conditioning subsystem, according to embodiments ofthe disclosure.

FIG. 22 illustrates a top view of the lighting assembly for a number ofgrow lines of receptacle supports (e.g., towers), according toembodiments of the disclosure.

FIG. 23 illustrates an irrigation subsystem according to embodiments ofthe disclosure.

FIG. 24 illustrates a flow sensor according to embodiments of thedisclosure.

FIGS. 25A and 25B illustrate digital thermometers, according toembodiments of the disclosure.

FIG. 26 illustrates a flow sensor assembly thermally coupled to a fluidchannel, according to embodiments of the disclosure.

FIG. 27 illustrates a flow sensor network, according to embodiments ofthe disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

The present description is made with reference to the accompanyingdrawings, in which various example embodiments are shown. However, manydifferent example embodiments may be used, and thus the descriptionshould not be construed as limited to the example embodiments set forthherein. Rather, these example embodiments are provided so that thisdisclosure will be thorough and complete. Various modifications to theexemplary embodiments will be readily apparent to those skilled in theart, and the generic principles defined herein may be applied to otherembodiments and applications without departing from the spirit and scopeof the disclosure. Thus, this disclosure is not intended to be limitedto the disclosed embodiments, but is to be accorded the widest scopeconsistent with the claims and the principles and features disclosedherein.

Exemplary Indoor Agricultural System

The following describes a vertical farm production system configured forhigh density growth and crop yield. Although embodiments of thedisclosure will primarily be described in the context of a vertical farmin which plants are grown in towers, those skilled in the art willrecognize that the principles described herein are not limited to avertical farm or the use of grow towers, but rather apply to plantsgrown in any structural arrangement.

FIGS. 1 and 2 illustrate a controlled environment agriculture system 10,according to embodiments of the disclosure. At a high level, the system10 may include an environmentally-controlled growing chamber 20, avertical tower conveyance system 200 that is disposed within the growingchamber 20 and configured to convey vertical grow towers with cropsdisposed therein, and a central processing facility 30. The plantvarieties that may be grown may be gravitropic/geotropic, phototropic,hydroponic, or some combination thereof. The varieties may varyconsiderably and include various leaf vegetables, fruiting vegetables,flowering crops, fruits, and the like. The controlled environmentagriculture system 10 may be configured to grow a single crop type at atime or to grow multiple crop types concurrently.

The system 10 may also include conveyance systems for moving the growtowers in a circuit throughout the crop's growth cycle, the circuitcomprising a staging area configured to load the grow towers into andout of the vertical tower conveyance mechanism 200. The centralprocessing system 30 may include one or more conveyance mechanisms fordirecting grow towers to stations in the central processing system 30,e.g., stations for loading plant plugs into, and harvesting crops from,the grow towers. The vertical tower conveyance system 200 is configuredto support and translate one or more grow towers 50 along grow lines202. According to embodiments of the disclosure, the grow towers 50 hangfrom the grow lines 202.

Each grow tower 50 is configured to contain plant growth media thatsupports a root structure of at least one crop plant growing therein.Each grow tower 50 is also configured to releasably attach to a growline 202 in a vertical orientation and move along the grow line 202during a growth phase. Together, the vertical tower conveyance mechanism200 and the central processing system 30 (including associatedconveyance mechanisms) can be arranged in a production circuit undercontrol of one or more computing systems.

The growth environment 20 may include light emitting sources positionedat various locations between and along the grow lines 202 of thevertical tower conveyance system 200. The light emitting sources can bepositioned laterally relative to the grow towers 50 in the grow line 202and configured to emit light toward the lateral faces of the grow towers50, which include openings from which crops grow. The light emittingsources may be incorporated into a water-cooled, LED lighting system asdescribed in U.S. Publication No. 2017/0146226A1, the disclosure ofwhich is incorporated by reference in its entirety herein. In such anembodiment, the LED lights may be arranged in a bar-like structure. Thebar-like structure may be placed in a vertical orientation to emit lightlaterally to substantially the entire length of adjacent grow towers 50.Multiple light bar structures may be arranged in the growth environment20 along and between the grow lines 202. Other lighting systems andconfigurations may be employed. For example, the light bars may bearranged horizontally between grow lines 202.

The growth environment 20 may also include a nutrient supply systemconfigured to supply an aqueous crop nutrient solution to the crops asthey translate through the growth chamber 20. The nutrient supply systemmay apply aqueous crop nutrient solution to the top of the grow towers50. Gravity may cause the solution travel down the vertically-orientedgrow tower 50 and through the length thereof to supply solution to thecrops disposed along the length of the grow tower 50. The growthenvironment 20 may also include an airflow source that is configured to,when a tower is mounted to a grow line 202, direct airflow in thelateral growth direction of growth and through an under-canopy of thegrowing plant, so as to disturb the boundary layer of the under-canopyof the growing plant. In other implementations, airflow may come fromthe top of the canopy or orthogonal to the direction of plant growth.The growth environment 20 may also include a control system, andassociated sensors, for regulating at least one growing condition, suchas air temperature, airflow speed, relative air humidity, and ambientcarbon dioxide gas content. The control system may for example includesuch sub-systems as HVAC units, chillers, fans and associated ductingand air handling equipment. Grow towers 50 may have identifyingattributes (such as bar codes or RFID tags). The controlled environmentagriculture system 10 may include corresponding sensors and programminglogic for tracking the grow towers 50 during various stages of the farmproduction cycle or for controlling one or more conditions of the growthenvironment. The operation of control system and the length of timetowers remain in the growth environment can vary considerably dependingon a variety of factors, such as crop type and other factors.

The grow towers 50 with newly transplanted crops or seedlings aretransferred from the central processing system 30 into the verticaltower conveyance system 200. Vertical tower conveyance system 200 movesthe grow towers 50 along respective grow lines 202 in growth environment20 in a controlled fashion. Crops disposed in grow towers 50 are exposedto the controlled conditions of the growth environment (e.g., light,temperature, humidity, air flow, aqueous nutrient supply, etc.). Thecontrol system is capable of automated adjustments to optimize growingconditions within the growth chamber 20 and make continuous improvementsto various attributes, such as crop yields, visual appeal and nutrientcontent. In addition, US Patent Publication Nos. 2018/0014485 and2018/0014486, incorporated by reference herein, describe application ofmachine learning and other operations to optimize grow conditions in avertical farming system. In some implementations, environmentalcondition sensors may be disposed on grow towers 50 or at variouslocations in the growth environment 20. When crops are ready forharvesting, grow towers 50 with crops to be harvested are transferredfrom the vertical tower conveyance system 200 to the central processingsystem 30 for harvesting and other processing operations.

Central processing system 30 may include processing stations directed toinjecting seedlings into towers 50, harvesting crops from towers 50, andcleaning towers 50 that have been harvested. Central processing system30 may also include conveyance mechanisms that move towers 50 betweensuch processing stations. For example, as FIG. 1 illustrates, centralprocessing system 30 may include harvester station 32, washing station34, and transplanter station 36. Harvester station 32 may depositharvested crops into food-safe containers and may include a conveyancemechanism for conveying the containers to post-harvesting facilities(e.g., preparation, washing, packaging and storage).

Controlled environment agriculture system 10 may also include one ormore conveyance mechanisms for transferring grow towers 50 betweengrowth environment 20 and central processing system 30. In theimplementation shown, the stations of central processing system 30operate on grow towers 50 in a horizontal orientation. In oneimplementation, an automated pickup (loading) station 43, and associatedcontrol logic, may be operative to releasably grasp a horizontal towerfrom a loading location, rotate the tower to a vertical orientation andattach the tower to a transfer station for insertion into a selectedgrow line 202 of the growth environment 20. On the other end of growthenvironment 20, automated laydown (unloading) station 41, and associatedcontrol logic, may be operative to releasably grasp and move avertically oriented grow tower 50 from a buffer location, rotate thegrow tower 50 to a horizontal orientation and place it on a conveyancesystem for loading into harvester station 32. In some implementations,if a grow tower 50 is rejected due to quality control concerns, theconveyance system may bypass the harvester station 32 and carry the growtower to washing station 34 (or some other station). The automatedlaydown and pickup stations 41 and 43 may each comprise a six-degrees offreedom robotic arm, such as a FANUC robot. The stations 41 and 43 mayalso include end effectors for releasably grasping grow towers 50 atopposing ends.

Growth environment 20 may also include automated loading and unloadingmechanisms for inserting grow towers 50 into selected grow lines 202 andunloading grow towers 50 from the grow lines 202. According toembodiments of the disclosure, a load transfer conveyance mechanism 47may include a powered and free conveyor system that conveys carriageseach loaded with a grow tower 50 from the automated pickup station 43 toa selected grow line 202. Vertical grow tower conveyance system 200 mayinclude sensors (such as RFID or bar code sensors) to identify a givengrow tower 50 and, under control logic, select a grow line 202 for thegrow tower 50. The load transfer conveyance mechanism 47 may alsoinclude one or more linear actuators that pushes the grow tower 50 ontoa grow line 202. Similarly, the unload transfer conveyance mechanism 45may include one or more linear actuators that push or pull grow towersfrom a grow line 202 onto a carriage of another powered and freeconveyor mechanism, which conveys the carriages 1202 from the grow line202 to the automated laydown station 41.

FIG. 12 illustrates a carriage 1202 that may be used in a powered andfree conveyor mechanism. In the implementation shown, carriage 1202includes hook 1204 that engages hook 52 of grow tower 50. A latchassembly 1206 may secure the grow tower 50 while it is being conveyed toand from locations in the system. In one implementation, one or both ofload transfer conveyance mechanism 47 and unload transfer conveyancemechanism 45 may be configured with a sufficient track distance toestablish a zone where grow towers 50 may be buffered. For example,unload transfer conveyance mechanism 45 may be controlled such that itunloads a set of towers 50 to be harvested unto carriages 1202 that aremoved to a buffer region of the track. On the other end, automatedpickup station 43 may load a set of towers to be inserted into growthenvironment 20 onto carriages 1202 disposed in a buffer region of thetrack associated with load transfer conveyance mechanism 47.

Grow Towers

Grow towers 50 provide the sites for individual crops to grow in thesystem. As FIGS. 3A and 3B illustrate, a tower 50 includes a hook 52 atthe top. Hook 52 allows grow tower 50 to be supported by a grow line 202when it is inserted into the vertical tower conveyance system 200. Inone implementation, a grow tower 50 measures 5.172 meters long, wherethe extruded length of the tower is 5.0 meters, and the hook is 0.172meters long. The extruded rectangular profile of the grow tower 50, inone implementation, measures 57 mm×93 mm (2.25″×3.67″). The hook 52 canbe designed such that its exterior overall dimensions are not greaterthan the extruded profile of the grow tower 50. The dimensions of growtower 50 can be varied depending on a number of factors, such as desiredthroughput, overall size of the system, and the like.

Grow towers 50 may include a set of grow sites 53 arrayed along at leastone face of the grow tower 50. In the implementation shown in FIG. 4A,grow towers 50 include grow sites 53 on opposing faces such that plantsprotrude from opposing sides of the grow tower 50. Transplanter station36 may transplant seedlings into empty grow sites 53 of grow towers 50,where they remain in place until they are fully mature and ready to beharvested. In one implementation, the orientation of the grow sites 53are perpendicular to the direction of travel of the grow towers 50 alonggrow line 202. In other words, when a grow tower 50 is inserted into agrow line 202, plants extend from opposing faces of the grow tower 50,where the opposing faces are parallel to the direction of travel.Although a dual-sided configuration is preferred, the invention may alsobe utilized in a single-sided configuration where plants grow along asingle face of a grow tower 50.

U.S. application Ser. No. 15/968,425 filed on May 1, 2018, which isincorporated by reference herein for all purposes, discloses an exampletower structure configuration that can be used in connection withvarious embodiments of the disclosure. In the implementation shown, growtowers 50 may each comprise three extrusions which snap together to formone structure. As shown, the grow tower 50 may be a dual-sidedhydroponic tower, where the tower body 103 includes a central wall 56that defines a first tower cavity 54 a and a second tower cavity 54 b.FIG. 4B provides a perspective view of an exemplary dual-sided,multi-piece hydroponic grow tower 50 in which each front face plate 101is hingeably coupled to the tower body 103. In FIG. 4B, each front faceplate 101 is in the closed position. The cross-section of the towercavities 54 a, 54 b may be in the range of 1.5 inches by 1.5 inches to 3inches by 3 inches, where the term “tower cavity” refers to the regionwithin the body of the tower and behind the tower face plate. The wallthickness of the grow towers 50 maybe within the range of 0.065 to 0.075inches. A dual-sided hydroponic tower, such as that shown in FIGS. 4Aand 4B, has two back-to-back cavities 54 a and 54 b, each preferablywithin the noted size range. In the configuration shown, the grow tower50 may include (i) a first V-shaped groove 58 a running along the lengthof a first side of the tower body 103, where the first V-shaped grooveis centered between the first tower cavity and the second tower cavity;and (ii) a second V-shaped groove 58 b running along the length of asecond side of the tower body 103, where the second V-shaped groove iscentered between the first tower cavity and the second tower cavity. TheV-shaped grooves 58 a, 58 b may facilitate registration, alignmentand/or feeding of the towers 50 by one or more of the stations incentral processing system 30.

U.S. application Ser. No. 15/968,425 discloses additional detailsregarding the construction and use of towers that may be used inembodiments of the disclosure. Another attribute of V-shaped grooves 58a, 58 b is that they effectively narrow the central wall 56 to promotethe flow of aqueous nutrient solution centrally where the plant's rootsare located. Other implementations are possible. For example, a growtower 50 may be formed as a unitary, single extrusion, where thematerial at the side walls flex to provide a hinge and allow thecavities to be opened for cleaning.

As FIGS. 4C and 4D illustrate, grow towers 50 may each include aplurality of receptacles 105, for example cut-outs 105 as shown, for usewith a compatible growth module 158, such as a plug holder. Each plugholder holds a plant of a given variety. Plug holder 158 may beultrasonically welded, bonded, or otherwise attached to tower face 101.As shown, the growth modules 158 may be oriented at a 45-degree anglerelative to the front face plate 101 and the vertical axis of the growtower 50. It should be understood, however, that tower design disclosedin the present application is not limited to use with a particular plugholder or orientation, rather, the towers disclosed herein may be usedwith any suitably sized or oriented growth module. As such, cut-outs 105are only meant to illustrate, not limit, the present tower design and itshould be understood that embodiments may employ towers with otherreceptacle designs. In particular, receptacle supports other than towersmay be used to support plants. In general, the receptacles may be partof any receptacle support structure for supporting plants within thegrow space. For example, the receptacles may be laid out in rows andcolumns in a horizontal plane. The receptacle support may comprise amember (e.g., a tray, a table, an arm) holding multiple receptacles in alongitudinal (e.g., row) direction. The receptacles may be conveyedduring their growth cycle in the longitudinal direction.

The use of a hinged front face plate simplifies manufacturing of growtowers, as well as tower maintenance in general and tower cleaning inparticular. For example, to clean a grow tower 50 the face plates 101are opened from the body 103 to allow easy access to the body cavity 54a or 54 b. After cleaning, the face plates 101 are closed. Since theface plates remain attached to the tower body 103 throughout thecleaning process, it is easier to maintain part alignment and to insurethat each face plate is properly associated with the appropriate towerbody and, assuming a double-sided tower body, that each face plate 101is properly associated with the appropriate side of a specific towerbody 103. Additionally, if the planting and/or harvesting operations areperformed with the face plate 101 in the open position, for thedual-sided configuration both face plates can be opened andsimultaneously planted and/or harvested, thus eliminating the step ofplanting and/or harvesting one side and then rotating the tower andplanting and/or harvesting the other side. In other embodiments,planting and/or harvesting operations are performed with the face plate101 in the closed position.

Other implementations are possible. For example, grow tower 50 cancomprise any tower body that includes a volume of medium or wickingmedium extending into the tower interior from the face of the tower(either a portion or individual portions of the tower or the entirety ofthe tower length. For example, U.S. Pat. No. 8,327,582, which isincorporated by reference herein, discloses a grow tube having a slotextending from a face of the tube and a grow medium contained in thetube. The tube illustrated therein may be modified to include a hook 52at the top thereof and to have slots on opposing faces, or one slot on asingle face.

Vertical Tower Conveyance System

FIG. 5A illustrates a portion of a grow line 202 in the vertical towerconveyance system 200. According to embodiments of the disclosure, thevertical tower conveyance system 200 includes grow lines 202 arranged inparallel. As discussed elsewhere herein, automated loading and unloadingmechanisms 45, 47 may selectively load and unload grow towers 50 from agrow line 202 under automated control systems. As shown, each grow line202 supports a plurality of grow towers 50. In one implementation, agrow line 202 may be mounted to the ceiling (or other support) of thegrow structure by a bracket for support purposes. Hook 52 hooks into,and attaches, a grow tower 50 to a grow line 202, thereby supporting thetower in a vertical orientation as it is translated through the verticaltower conveyance system 200. A conveyance mechanism moves towers 50attached to respective grow lines 202.

FIG. 10 illustrates the cross section or extrusion profile of a growline 202, according to embodiments of the disclosure. The grow line 202may be an aluminum extrusion. The bottom section of the extrusionprofile of the grow line 202 includes an upward facing groove 1002. AsFIG. 9 shows, hook 52 of a grow tower 50 includes a main body 53 andcorresponding member 58 that engages groove 1002 as shown in FIGS. 5Aand 8. These hooks allow the grow towers 50 to hook into the groove 1002and index along the grow line 202 as discussed below. Conversely, growtowers 50 can be manually unhooked from a grow line 202 and removed fromproduction. This ability may be necessary if a crop in a grow tower 50becomes diseased so that it does not infect other towers. In oneimplementation, the width of groove 1002 (for example, 13 mm) is anoptimization between two different factors. First, the narrower thegroove the more favorable the binding rate and the less likely growtower hooks 52 are to bind. Conversely, the wider the groove the slowerthe grow tower hooks wear due to having a greater contact patch.Similarly, the depth of the groove, for example 10 mm, may be anoptimization between space savings and accidental fallout of towerhooks.

Hooks 52 may be injection-molded plastic parts. In one implementation,the plastic may be polyvinyl chloride (PVC), acrylonitrile butadienestyrene (ABS), or an Acetyl Homopolymer (e.g., Delrin® sold by DuPontCompany). The hook 52 may be solvent bonded to the top of the grow tower50 and/or attached using rivets or other mechanical fasteners. Thegroove-engaging member 58 which rides in the rectangular groove 1002 ofthe grow line 202 may be a separate part or integrally formed with hook52. If separate, this part can be made from a different material withlower friction and better wear properties than the rest of the hook,such as ultra-high-molecular weight polyethylene or acetal. To keepassembly costs low, this separate part may snap onto the main body ofthe hook 52. Alternatively, the separate part also be over-molded ontothe main body of hook 52.

As FIGS. 6 and 10 illustrate, the top section of the extrusion profileof grow line 202 contains a downward facing t-slot 1004. Linear guidecarriages 610 (described below) ride within the t-slot 1004. The centerportion of the t-slot 1004 may be recessed to provide clearance fromscrews or over-molded inserts which may protrude from the carriages 610.Each grow line 202 can be assembled from a number of separatelyfabricated sections. In one implementation, sections of grow line 202are currently modeled in 5 to 6-meter lengths. Longer sections reducethe number of junctions but are more susceptible to thermal expansionissues and may significantly increase shipping costs. Additionalfeatures not captured by the figures include intermittent mounting holesto attach the grow line 202 to the ceiling structure and to attachirrigation lines. Interruptions to the t-slot 1004 may also be machinedinto the conveyor body. These interruptions allow the linear guidecarriages 610 to be removed without having to slide them all the way outthe end of a grow line 202.

At the junction between two sections of a grow line 202, a block 612 maybe located in the t-slots 1004 of both conveyor bodies. This blockserves to align the two grow line sections so that grow towers 50 mayslide smoothly between them. Alternative methods for aligning sectionsof a grow line 202 include the use of dowel pins that fit into dowelholes in the extrusion profile of the section. The block 612 may beclamped to one of the grow line sections via a set screw, so that thegrow line sections can still come together and move apart as the resultof thermal expansion. Based on the relatively tight tolerances and smallamount of material required, these blocks may be machined. Bronze may beused as the material for such blocks due to its strength, corrosionresistance, and wear properties.

In one implementation, the vertical tower conveyance system 200 utilizesa reciprocating linear ratchet and pawl structure (hereinafter referredto as a “reciprocating cam structure or mechanism”) to move grow towers50 along a grow line 202. FIGS. 5A, 6 and 7 illustrate one possiblereciprocating cam mechanism that can be used to move grow towers 50across grow lines 202. Pawls or “cams” 602 physically push grow towers50 along grow line 202. Cams 602 are attached to cam channel 604 (seebelow) and rotate about one axis. On the forward stroke, the rotation islimited by the top of the cam channel 604, causing the cams 602 to pushgrow towers 50 forward. On the reserve or back stroke, the rotation isunconstrained, thereby allowing the cams to ratchet over the top of thegrow towers 50. In this way, the cam mechanism can stroke a relativelyshort distance back and forth, yet grow towers 50 always progressforward along the entire length of a grow line 202. A control system, inone implementation, controls the operation of the reciprocating cammechanism of each grow line 202 to move the grow towers 50 according toa programmed growing sequence. In between movement cycles, the actuatorand reciprocating cam mechanism remain idle.

The pivot point of the cams 602 and the means of attachment to the camchannel 604 consists of a binding post 606 and a hex head bolt 608;alternatively, detent clevis pins may be used. The hex head bolt 608 ispositioned on the inner side of the cam channel 604 where there is notool access in the axial direction. Being a hex head, it can be accessedradially with a wrench for removal. Given the large number of camsneeded for a full-scale farm, a high-volume manufacturing process suchas injection molding is suitable. ABS is suitable material given itsstiffness and relatively low cost. All the cams 602 for a correspondinggrow line 202 are attached to the cam channel 604. When connected to anactuator, this common beam structure allows all cams 602 to stroke backand forth in unison. The structure of the cam channel 604, in oneimplementation, is a downward facing u-channel constructed from sheetmetal. Holes in the downward facing walls of cam channel 604 providemounting points for cams 602 using binding posts 606.

Holes of the cam channel 604, in one implementation, are spaced at 12.7mm intervals. Therefore, cams 602 can be spaced relative to one anotherat any integer multiple of 12.7 mm, allowing for variable grow towerspacing with only one cam channel. The base of the cam channel 604limits rotation of the cams during the forward stroke. All degrees offreedom of the cam channel 604, except for translation in the axialdirection, are constrained by linear guide carriages 610 (describedbelow) which mount to the base of the cam channel 604 and ride in thet-slot 1004 of the grow line 202. Cam channel 604 may be assembled fromseparately formed sections, such as sections in 6-meter lengths. Longersections reduce the number of junctions but may significantly increaseshipping costs. Thermal expansion is generally not a concern because thecam channel is only fixed at the end connected to the actuator. Giventhe simple profile, thin wall thickness, and long length needed, sheetmetal rolling is a suitable manufacturing process for the cam channel.Galvanized steel is a suitable material for this application.

Linear guide carriages 610 are bolted to the base of the cam channels604 and ride within the t-slots 1004 of the grow lines 202. In someimplementations, one carriage 610 is used per 6-meter section of camchannel. Carriages 610 may be injection molded plastic for low frictionand wear resistance. Bolts attach the carriages 610 to the cam channel604 by threading into over molded threaded inserts. If select cams 602are removed, these bolts are accessible so that a section of cam channel604 can be detached from the carriage and removed.

Sections of cam channel 604 are joined together with pairs of connectors616 at each joint; alternatively, detent clevis pins may be used.Connectors 616 may be galvanized steel bars with machined holes at 20 mmspacing (the same hole spacing as the cam channel 604). Shoulder bolts618 pass through holes in the outer connector, through the cam channel604, and thread into holes in the inner connector. If the shoulder boltsfall in the same position as a cam 602, they can be used in place of abinding post. The heads of the shoulder bolts 618 are accessible so thatconnectors and sections of cam channel can be removed.

In one implementation, cam channel 604 attaches to a linear actuator,which operates in a forward and a back stroke. A suitable linearactuator may be the T13-B4010MS053-62 actuator offered by Thomson, Inc.of Redford, Va.; however, the reciprocating cam mechanism describedherein can be operated with a variety of different actuators. The linearactuator may be attached to cam channel 604 at the off-loading end of agrow line 202, rather than the on-boarding end. In such a configuration,cam channel 604 is under tension when loaded by the towers 50 during aforward stroke of the actuator (which pulls the cam channel 604) whichreduces risks of buckling. FIG. 7A illustrates operation of thereciprocating cam mechanism according to embodiments of the disclosure.In step A, the linear actuator has completed a full back stroke; as FIG.7A illustrates, one or more cams 602 may ratchet over the hooks 52 of agrow tower 50. Step B of FIG. 7A illustrates the position of cam channel604 and cams 602 at the end of a forward stroke. During the forwardstroke, cams 602 engage corresponding grow towers 50 and move them inthe forward direction along grow line 202 as shown. Step C of FIG. 7Aillustrates how a new grow tower 50 (Tower 0) may be inserted onto agrow line 202 and how the last tower (Tower 9) may be removed. Step Dillustrates how cams 602 ratchet over the grow towers 50 during a backstroke, in the same manner as Step A. The basic principle of thisreciprocating cam mechanism is that reciprocating motion from arelatively short stroke of the actuator transports towers 50 in onedirection along the entire length of the grow line 202. Morespecifically, on the forward stroke, all grow towers 50 on a grow line202 are pushed forward one position. On the back stroke, the cams 602ratchet over an adjacent tower one position back; the grow towers remainin the same location. As shown, when a grow line 202 is full, a new growtower may be loaded and a last tower unloaded after each forward strokeof the linear actuator. In some implementations, the top portion of thehook 52 (the portion on which the cams push), is slightly narrower thanthe width of a grow tower 50. As a result, cams 602 can still engagewith the hooks 52 when grow towers 50 are spaced immediately adjacent toeach other. FIG. 7A shows 9 grow towers for didactic purposes. A growline 202 can be configured to be quite long (for example, 40 meters)allowing for a much greater number of towers 50 on a grow line 202 (suchas 400-450). Other implementations are possible. For example, theminimum tower spacing can be set equal to or slightly greater than twotimes the side-to-side distance of a grow tower 50 to allow more thanone grow tower 50 to be loaded onto a grow line 202 in each cycle.

Still further, as shown in FIG. 7A, the spacing of cams 602 along thecam channel 604 can be arranged to effect one-dimensional plant indexingalong the grow line 202. In other words, the cams 602 of thereciprocating cam mechanism can be configured such that spacing betweentowers 50 increases as they travel along a grow line 202. For example,spacing between cams 602 may gradually increase from a minimum spacingat the beginning of a grow line to a maximum spacing at the end of thegrow line 202. This may be useful for spacing plants apart as they growto increase light interception and provide spacing, and, throughvariable spacing or indexing, increasing efficient usage of the growthchamber 20 and associated components, such as lighting. In oneimplementation, the forward and back stroke distance of the linearactuator is equal to (or slightly greater than) the maximum towerspacing. During the back stroke of the linear actuator, cams 602 at thebeginning of a grow line 202 may ratchet and overshoot a grow tower 50.On the forward stroke, such cams 602 may travel respective distancesbefore engaging a tower, whereas cams located further along the growline 202 may travel shorter distances before engaging a tower or engagesubstantially immediately. In such an arrangement, the maximum towerspacing cannot be two times greater than the minimum tower spacing;otherwise, a cam 602 may ratchet over and engaging two or more growtowers 50. If greater maximum tower spacing is desired, an expansionjoint may be used, as illustrated in FIG. 7B. An expansion joint allowsthe leading section of the cam channel 604 to begin traveling before thetrailing end of the cam channel 604, thereby achieving a long stroke. Inparticular, as FIG. 7B shows, expansion joint 710 may attach to sections604 a and 604 b of cam channel 604. In the initial position (702), theexpansion joint 710 is collapsed. At the beginning of a forward stroke(704), the leading section 604 a of cam channel 604 moves forward (asthe actuator pulls on cam channel 604), while the trailing section 604 bremains stationary. Once the bolt bottoms out on the expansion joint 710(706), the trailing section 604 of cam channel 604 begins to moveforward as well. On the back stroke (708), the expansion joint 710collapses to its initial position.

Other implementations for moving vertical grow towers 50 may beemployed. For example, a lead screw mechanism may be employed. In suchan implementation, the threads of the lead screw engage hooks 52disposed on grow line 202 and move grow towers 50 as the shaft rotates.The pitch of the thread may be varied to achieve one-dimensional plantindexing. In another implementation, a belt conveyor include paddlesalong the belt may be employed to move grow towers 50 along a grow line202. In such an implementation, a series of belt conveyors arrangedalong a grow line 202, where each belt conveyor includes a differentspacing distance among the paddles to achieve one-dimensional plantindexing. In yet other implementations, a power-and-free conveyor may beemployed to move grow towers 50 along a grow line 202.

Other configurations for grow line 202 are possible. For example,although the grow line 202 illustrated in the various figures ishorizontal to the ground, the grow line 202 may be sloped at a slightangle, either downwardly or upwardly relative to the direction of towertravel. Still further, while the grow line 202 described above operatesto convey grow towers in a single direction, the grow line 202 may beconfigured to include multiple sections, where each section is orientedin a different direction. For example, two sections may be perpendicularto each other. In other implementations, two sections may run parallelto each other, but have opposite directions of travel, to form asubstantially u-shaped travel path. In such an implementation, a returnmechanism can transfer grow towers from the end of the first pathsection to the onload end of the second path section of the grow line.

Irrigation & Aqueous Nutrient Supply System

FIG. 13 is a functional block diagram setting forth the components of anirrigation system according to embodiments of the disclosure. In theimplementation shown, the irrigation system 1300 is a closed-loop systemcomprising a recirculation tank 1302 that both supplies nutrientsolution to grow towers 50 and receives excess or remaining nutrientsolution returning from the grow towers 50. In the particularimplementation shown, supply pump 1304 pumps aqueous nutrient solutionfrom recirculation tank 1302 to one or more irrigation lines 1306disposed above grow towers 1308. Gutter 1310 recovers excess aqueousnutrient solution that drops from grow towers 1308. A return pump 1312returns excess aqueous nutrient solution to the screen filter, whichthen returns clean water to the recirculation tank 1302.

As FIG. 13 illustrates, irrigation system 1300 may include one or morecomponents for conditioning or treating the aqueous nutrient solution,as well as sensing conditions at various points in the irrigation loop.For example, return filter 1314 may filter debris and other particulatematter prior to returning excess aqueous nutrient solution to therecirculation tank 1302. In one implementation, return filter may be a150 micrometer, parabolic screen filter; however, other filters, such asmedia and disc filters, can be used depending on the particularapplication and expected particle size and quantity in excess aqueousnutrient solution. In some implementations, recirculation tank 1302 mayinclude cooling cools. Chiller loop 1330 supplies cooling fluid throughthe coils to facilitate achieving a target temperature for the aqueousnutrient solution to be supplied to irrigation line 1306.

Crops in grow towers 50 will generally take up nutrients from aqueousnutrient solution, thereby lowering nutrient levels in the excessnutrient solution returning to recirculation tank 1302. Irrigationsystem 1300 may also include nutrient and pH dosing system 1340, ionsensor 1342 and tank level sensor 1344. During operation, ion sensor1342 may sample the nutrient solution at a predefined interval. Duringsampling, ion sensor 1342 may check the ion levels of 8 separatenutrients and compare them to desired nutrient levels. Ion sensor 1342may be an 8-ion analyzer offered by CleanGrow Sensors of Wolverhampton,United Kingdom. Responsive to detected nutrient levels, nutrient and pHdosing system 1350 may inject a single element type dose to be deliveredto the recirculation tank 1302, based on the nutrient mix desired, andthe room available in the tank (as sensed by tank level sensor 1344, forthe water needed to transport the dose). In some implementations,nutrient and pH dosing system 1350 may use the sensed nutrient data anda desired nutrient recipe to calculate a nutrient adjustment mix toadjust the nutrient levels of recirculation tank 1302, using thesmallest available volume in the tank. Nutrient and pH dosing system1340 may include one or more venturi injectors for dosing particularnutrient solutions into the irrigation loop. In one implementation,nutrient and pH dosing system 1340 is an AMI Penta Fertilizer Mixer unitoffered by Senmatic A/S of Sanderso, Denmark.

Irrigation system 1300 may also include pressure transducer 1314 andflow sensor 1316 to monitor irrigation loop conditions and control theoperation of supply pump 1304. According to embodiments of thedisclosure, flow sensors 1316 may also be located in or near air supplyducts or nutrient water returns (e.g., gutters). Irrigation system 1300may also use water from condensate collection mechanism 1348, in oneimplementation as a primary source of water for the nutrient water.Condensate collection mechanism 1348 recaptures condensate in the aircontained within growth environment 20 using, in one implementation,mechanical dehumidification. Reverse osmosis system 1346 filters waterreceived from an external water source, such as a municipal watersystem, to the extent irrigation system 1300 requires additional water.In some implementations, reverse osmosis system 1346 may also filterwater received from condensate collection mechanism 1346. Irrigationsystem 1300 may also include components for ozone treatment and cleaningof aqueous nutrient solution. For example, ozone pump 1352 suppliesaqueous nutrient solution to ozone treatment tank 1356 filtered byfilter 1354. Bypass valve 1358 can be used to redirect ozone injectedwater to treat the screen filter.

Irrigation system 1300 may also include in-line pH dosing system 1318and 5-in-1 sensor 1320. 5-in-1 sensor samples temperature, pH,Electrical Conductivity (EC), dissolved oxygen and oxidization reductionpotential of aqueous nutrient solution. In-line pH dosing system 1318can make micro-adjustments to pH levels based on sensed pH in theirrigation loop. The cooling loop 1380 may be controlled based on thetemperature that is read by 5-1 sensor 1320. Irrigation system 1300 mayalso include bypass valve 1322 to allow the irrigation supply, sensingcomponents, and/or the filter to run without aqueous nutrient solutionreaching irrigation line 1306. Bypass valve 1322 can be used to testirrigation system 1300 and/or use bypass valve 1322 to divert aqueousnutrient solution from irrigation line 1306 until desired pH and otherconditions are met.

FIG. 8 illustrates how an irrigation line 802 may be attached to growline 202 to supply an aqueous nutrient solution to crops disposed ingrow towers 50 as they translate through the vertical tower conveyancesystem 200. Irrigation line 802, in one implementation, is a pressurizedline with spaced-apart apertures disposed at the expected locations ofthe grow towers 50 as they advance along grow line 202 with eachmovement cycle. For example, the irrigation line 802 may be a polyvinylchloride (PVC) pipe having an inner diameter of 0.75 inches and holeshaving diameters of 0.125 inches. The irrigation line 802 may beapproximately 40 meters in length spanning the entire length of a growline 202. To ensure adequate pressure across the entire line, irrigationline 802 may be broken into shorter sections, each connected to amanifold, so that pressure drop is reduced and to achieve consistentflow rate across a line. Nutrient water delivery to the sections can becontrolled with solenoid or on/off valves to allow for water to besupplied to only some subset of the grow towers 50 in a grow line 202.

As FIG. 8 shows, a funnel structure 902 collects aqueous nutrientsolution from irrigation line 802 and distributes the aqueous nutrientsolution to the cavity(ies) 54 a, 54 b of the grow tower 50 as discussedin more detail below. FIGS. 9 and 11A illustrate that the funnelstructure 902 may be integrated into hook 52. For example, the funnelstructure 902 may include a collector 910, first and second passageways912 and first and second slots 920. As FIG. 9 illustrates, thegroove-engaging member 58 of the hook may disposed at a centerline ofthe overall hook structure. The funnel structure 902 may include flangesections 906 extending downwardly opposite the collector 910 and onopposing sides of the centerline. The outlets of the first and secondpassageways are oriented substantially adjacent to and at opposing sidesof the flange sections 906, as shown. Flange sections 906 register withcentral wall 56 of grow tower 50 to center the hook 52 and providesadditional sites to adhere or otherwise attach hook 52 to grow tower 50.In other words, when hook 52 is inserted into the top of grow tower 50,central wall 56 is disposed between flange sections 906. In theimplementation shown, collector 910 extends laterally from the main body53 of hook 52.

As FIG. 11B shows, funnel structure 902 includes a collector 910 thatcollects nutrient fluid and distributes the fluid evenly to the innercavities 54 a and 54 b of tower through passageways 912. Passageways 912are configured to distribute aqueous nutrient solution near the centralwall 56 and to the center back of each cavity 54 a, 54 b over the endsof the plug holders 158 and where the roots of a planted crop areexpected. As FIG. 11C illustrates, in one implementation, the funnelstructure 902 includes slots 920 that promote the even distribution ofnutrient fluid to both passageways 912. For nutrient solution to reachpassageways 912, it must flow through one of the slots 920. Each slot920 may have a V-like configuration where the width of the slot openingincreases as it extends from the substantially flat bottom surface 922of collector 910. For example, each slot 920 may have a width of 1millimeter at the bottom surface 922. The width of slot 920 may increaseto 5 millimeters over a height of 25 millimeters. The configuration ofthe slots 920 causes nutrient fluid supplied at a sufficient flow rateby irrigation line 802 to accumulate in collector 910, as opposed toflowing directly to a particular passageway 912, and flow through slots920 to promote even distribution of nutrient fluid to both passageways912.

Other implementations are possible. For example, the funnel structuremay be configured with two separate collectors that operate separatelyto distribute aqueous nutrient solution to a corresponding cavity 54 a,54 b of a grow tower 50. In such a configuration, the irrigation supplyline can be configured with one hole for each collector. In otherimplementations, the towers may only include a single cavity and includeplug containers only on a single face 101 of the towers. Such aconfiguration still calls for a use of a funnel structure that directsaqueous nutrient solution to a desired middle and back portion of thetower cavity, but obviates the need for separate collectors or otherstructures facilitating even distribution.

In operation, irrigation line 802 provides aqueous nutrient solution tofunnel structure 902 that evenly distributes the water to respectivecavities 54 a, 54 b of grow tower 50. The aqueous nutrient solutionsupplied from the funnel structure 902 irrigates crops contained inrespective plug containers 158 as it trickles down. In oneimplementation, a gutter disposed under each grow line 202 collectsexcess aqueous nutrient solution from the grow towers 50 for recycling.In one implementation, the width of the gutter can be configured to belarger than the width of the grow towers 50 but narrow enough to act asa guide to prevent grow towers 50 from swinging. For example, the widthof the gutter can be 0.5 inches larger than the width of the grow towers50, and the walls of the gutter can be configured to extend an inch ormore higher than the bottom of grow towers 50.

The apertures of irrigation line 802 can simply be holes drilled (orotherwise machined) into the pipe structure. Water, however, has apropensity to wick onto the surface of the pipe as it exits theapertures causing water to run along the pipe and drip down outside thefunnel structure of the grow towers. In some implementations, theapertures can include structures directed to reducing or controllingpossible leakage caused by the foregoing. For example, the apertures maybe drilled holes with slotted spring pins pressed in, drilled holes withcoiled spring pins pressed in, and drilled holes with a custom machinedfeature around the circumference made from a custom mill tool. All threeof the solutions above are intended to create a sharp lip at the exit ofthe hole such that water cannot run along the pipe. Still further,separate emitters can be used at the select positions along the growline 202.

Other solutions are possible. For example, an injection molded part witha sharp lip may be configured to snap into the aperture or hole drilledinto the irrigation line pipe. FIG. 16A is a section view of anirrigation line 802 including a nozzle 1602 attached to and extendingfrom an aperture in irrigation line 802. FIG. 16B is a perspective viewof nozzle 1602 attached to a section of irrigation line 802. FIG. 16C isa section view of nozzle 1602. As shown in FIGS. 16A and 16B, nozzle1602 may include flanges 1604 to facilitate location and placement ofnozzle 1602 in the apertures of irrigation line 802. In oneimplementation, nozzle 1602 may also include a small ridge or detentthat engages the edge of the aperture at the inner surface of irrigationline 802 to allow nozzle 1602 to be snapped into place. Adhesives orultrasonic welding can be used in addition to, or in lieu of, the smallridge to secure nozzle 1602. As the various figures show, nozzle 1602includes a chamfered edge at the tip 1606 of nozzle 1602 to create asharp transition to reduce water from wicking onto the outer surface ofnozzle 1602. The upper portion 1608 of nozzle 1602 extending withinirrigation line 802 may include a notch or slot 1610 to facilitate flowof nutrient solution out of irrigation line 802. Other implementationsare possible. As shown in FIG. 16D for example, instead of pressing intoa hole in the irrigation line 802, a nozzle 1603 may include threads1605 which thread into a tapped hole of irrigation line 802. A seal maybe formed between the threads of the nozzle and the line 802 and aidedby a PTFE sealant (either thread tape or a paste). Such a nozzle 1603may have a hexagonal portion 1607 extending along its body which allowsit to be installed with a hexagonal drive tool.

In one implementation, each aperture of irrigation line 802 may befitted with nozzle 1602. In other implementations, the apertures at thesecond end (the end opposite the first end) of an irrigation line 802(or the end of a section of irrigation line 802) may include analternative nozzle 1702 including an air-bleed feature illustrated inFIGS. 17A, 17B and 17C. The air-bleed feature promotes consistent flowthroughout irrigation line 802, as discussed in more detail below. Inthe implementation shown, the lower portion of nozzle 1702 issubstantially the same as nozzle 1602. The upper portion 1708 of nozzle1702 extends further into the interior of irrigation line 802 andincludes slot 1810 and slit 1712. The extended upper portion 1708facilitates bleeding air from irrigation line 802. Slit 1712 affordsmore room for water and air to facilitate their flow out of nozzle 1702.

FIG. 18 is a schematic diagram illustrating an irrigation line forpurposes of describing operation of the air-bleed feature describedabove. In various implementations, the irrigation system runs on aperiodic basis in that the irrigation system is at rest betweenirrigation cycles. Between irrigation cycles, air fills the irrigationline 802 as the nutrient solution has drained off. At the beginning ofan irrigation cycle (as the nutrient flow front moves into a section ofirrigation line 802), air is pushed out of each nozzle 1602 until thenutrient solution passes a given nozzle. Once the front passes a givennozzle 1602, the nutrient solution starts to flow through the nozzle1602 (instead of air). Nozzle N is the last nozzle to switch from airflow to nutrient flow. With this model for the nutrient flow when theirrigation cycle is started, the air flow though nozzle N should be thesame if the upper portion of the last nozzle is short (i.e., matchingnozzles (1602) 1, 2, . . . , N−1) or tall (to permit air venting) up tothe time just before the nutrient front reaches nozzle N.

When the irrigation cycle begins and nutrient solution enters irrigationline 802, the solution pushes the air in the irrigation line 802 to theend of the line where it builds as one large pocket. With a nozzlehaving a shorter upper portion 1608, some of this air exits, but as theair is pushed out, water begins to cover the last (N) nozzle driving theair pocket above the water and above the last aperture. A newequilibrium is then obtained with water trickling out of the lastaperture and a pocket of air sitting above the water. The air is thentrapped and continues to exist in the line. Because the air takes up avolume, it prevents water from fully filling the irrigation line 802thus creating flow out for the last aperture which is much less than atall other sites. Depending on the size of this air pocket, this weakerflow may exist for apertures (N−1, N−2, etc.) prior to the last (N) aswell. The taller upper portion 1708 of nozzle 1702 allows for air to beconstantly drained (i.e., small volumes of air at more frequentintervals). Because the top of the nozzle 1702 is at the top of innersurface of irrigation line 802 were the air pocket is located, air canalways drain from this nozzle independently from the amount of water inthe line. Unlike the shorter nozzle where a pocket of air may be trappedabove the water in the line 802 and never able to exit (driving poorflow behavior), the longer nozzle 1702 allows air to more freely exit.In one implementation, the irrigation system supplies nutrient solutionat a first end of the irrigation line 802. In such an implementation,nozzle 1702 is attached proximal to the second end of irrigation line802 (or section of irrigation line 802). In other implementations, theirrigation system supplies nutrient solution to a middle portion of theirrigation line 802. In such an implementation, nozzle 1702 may beinstalled at both ends of irrigation line 802 (or sections thereof).

FIG. 14A illustrates an example gutter 1402 that can be disposed under agrow line 202 to collect excess aqueous nutrient solution from growtowers 50 attached to the grow line 202. In the implementation shown,gutter 1402 has a gradually-sloped (e.g., a 0.5% slope) bottom thatcauses excess nutrient solution to collect at end basin structure 1404.FIGS. 14B and 14C show end structure 1404 in more detail. As FIGS. 14Band 14C illustrate, basin structure 1404 couples to the low end ofgutter 1402 and includes an outlet 1406 to which a pipe, barb, or otherstructure attaches. As FIG. 13 illustrates, return pump 1312 operablyconnects with a hose, or pipe, to end structure 1404 to pump excessaqueous nutrient solution back to recirculation tank 1302, as discussedabove. The return pump 1312 may be controlled by utilizing an ultrasonicsensor to maintain a certain water level in the gutter as well as a pumpoutlet pressure in order for the nutrient solution to return to thefilter on the skid.

Gutter 1402 may consist of multiple separate sections that are joinedtogether to form a unitary structure. FIGS. 14D and 14E illustrate anexample gutter section 1408 according to embodiments of the disclosure.Gutter section 1408 may comprise a main body 1410 and flanges 1412. AsFIG. 14E illustrates, the bottom 1414 of gutter section is sloped. AsFIG. 14A shows, multiple gutter sections are joined at respectiveflanges 1412 to create gutter 1402. In one implementation, gasketsbetween flanges of adjoining gutter sections can be used to achieve awater tight seal. Flanges 1412 may also include feet sections tofacilitate securing the gutter to a floor or other structure. As FIG.14A further illustrates, gutter sections are similar to each other, butnot identical. For example, the initial height of bottom 1414 of a givengutter section 1408 substantially matches the ending height of thebottom of an adjoining gutter structure. Similarly, the ending height ofbottom 1414 of the gutter structure 1408 substantially matches theinitial height of the adjoining gutter section. In this manner, theoverall structure achieves a substantially continuous slope causingexcess aqueous nutrient solution to flow to end structure 1404 forrecirculation or disposal.

In one implementation, each grow line 202 is supported by a separateirrigation loop or zone that operates independently of irrigation loopsassociated with other grow lines in growth environment 20. In oneimplementation, each irrigation loop is supported by an irrigation skidthat includes many of the components set forth in FIG. 13. Use of anirrigation skid allows for partial fabrication of the irrigation loopoff site to lower overall costs of creating the crop production system.FIGS. 15A and 15B illustrate an irrigation skid 1500 according toembodiments of the disclosure. As FIGS. 15A and 15B illustrate,irrigation skid 1500 includes a frame 1502 onto which various irrigationcomponents are mounted, such as recirculation tank 1504. In oneimplementation, irrigation skid 1500 also includes supply pump 1506,ozone supply pump 1508, and in-line pH dosing pump 1510. Irrigation skid1500 also includes plumbing, valves, sensors, a filter, cooling coil,electrical and control components to connect and operate the irrigationloop. In one implementation, other components illustrated in FIG. 13 mayoperate or support multiple irrigation skids. For example, whileirrigation skid 1500 includes ozone supply pump 1508 and associatedplumbing, the remaining ozone cleaning components are separate from theskid and can be used to support multiple irrigation skids.

Nutrient and pH dosing system 1340, in one implementation, is operablyconnected to multiple irrigation skids 1500 by associated plumbing,valves and other controls. An irrigation control system controls valvesand associated plumbing components as needed to interface nutrient andpH dosing system 1340, and associated sensors, with a given irrigationskid 1500. The Nutrient and pH dosing system has the ability to purgeand rinse between dosing intervals, in order to prevent mixing ofnutrient water from one recirculating loop to another. During operation,the nutrient solution in each recirculating irrigation loop is sampledon a predefined interval for that specific loop. During sampling, theion levels of 8 separate nutrients may be checked and compared to thedesired nutrient levels for that specific loop. Nutrient and pH dosingsystem 1340 may inject a nutrient dose to be delivered to therecirculation tank 1504 for that loop, based on the nutrient mixrequired and the room available in the tank for the water needed totransport the dose.

FIG. 19 illustrates a plant growing environment 20 and an environmentalconditioning system 302 for conditioning air and fluid (e.g., water) inthe grow space 20, according to embodiments of the disclosure. The plantgrowing environment 20 includes at least one receptacle supportstructure 304 (such as a tower 50) having receptacles for holding plants306, and a fluid-cooled light fixture 308, according to embodiments ofthe disclosure.

An irrigation pump 309 circulates water and nutrients through the plantsupport structure 304. Carbon dioxide supply equipment 311 providescarbon dioxide to the plants. The irrigation pump 309 and carbon dioxidesupply equipment 311 may be considered as part of the conditioningsystem 302, according to embodiments of the disclosure.

According to embodiments of the disclosure, the conditioning system 302includes a dehumidifier 310, a fluid (e.g., water) conditioning system312, and a heating coil 314 in heat exchanger 315. The dehumidifier 310receives return air A from the grow space 101. The conditioning system302 provides supply air B, having a temperature and relative humiditythat is controlled to meet setpoints for desired operating conditions ofthe plants in the environment 20.

The fluid conditioning system 312 receives return fluid C from thefluid-cooled light fixture 308. According to embodiments of thedisclosures, the fluid conditioning system 312 can control the fluidtemperature by varying the fluid flow rate through the light fixtures308. The fluid conditioning system 312 supplies to the fluid-cooledlight fixture 308 a supply fluid D, having a temperature that iscontrolled to meet set points for desired operating conditions of theplants in the environment 20.

According to embodiments of the disclosure, waste heat from the fluidpassing through fluid conditioning system 312 may be provided to theheating coil 314 in the heat exchanger 315 to heat air E that is outputfrom the dehumidifier 310. The air heated by the coil 314 is output asheated air B to the grow space 20.

The controller 203 may control all the elements of the conditioningsystem 302, according to embodiments of the disclosure. The controller203 may be implemented using programmed logic, such as a computer, amicrocontroller, or an ASIC. The controller 203 may receive sensedparameters from sensors distributed throughout the plant growingenvironment 101 and the air and water conditioning system 302, accordingto embodiments of the disclosure. The sensors 204 may include sensorsthat sense environmental conditions such as temperature; humidity; airflow; CO₂; irrigation flow rate; pH, EC, DO, and nutrient levels ofirrigation water; and light intensity, spectrum, and schedule. Thecontroller 203 may use the sensed parameters as feedback to instruct theconditioning system 302 to control environmental treatments (e.g.,temperature, humidity) of the plant growing environment 101, accordingto embodiments of the disclosure.

FIG. 21 illustrates an enhanced HVAC system 2100 including an economizersubsystem 2102 and an air conditioning subsystem 2104, according toembodiments of the disclosure. The economizer subsystem 2102 includes anintake vent 2106, an exhaust fan 2108, supply air ducts 2110, and returnair ducts 2112. Each pair of supply and return air ducts 2110, 2112circulate air within a zone in the grow room 20. Each supply air duct2110 provides supply air SA. Each return air duct 2112 receives returnair RA. The supply air ducts 2110 run down the aisle between pairs ofgrow lines 202 (not shown in this figure) of hanging grow towers 50,according to embodiments of the disclosure. (Those skilled in the artwill recognize that “tower” and “receptacle support” may be usedinterchangeably herein as appropriate.)

The economizer 2102 includes an economizer intake damper XC01 2114 andan economizer exhaust damper XC03 2118. HVAC dampers FC04-FC09 2120control the supply of air from air conditioning subsystem 2104 to thegrow room zones. According to embodiments of the disclosure, thecontroller 203 may close the end dampers FC04 2120 and FC09 2120 atcertain times of the day to drive more airflow at different canopypositions for specific plants. Air conditioning subsystem 2104 operatessimilarly to conditioning system 302 of FIG. 19. Air conditioningsubsystem 2104 includes heat exchangers and HVAC supply fans 2202. Achiller 2204 provides hot and cold water to a dehumidifier system in theair conditioning subsystem.

The normal state of operation for the chiller 2204 provides both warmand cold water to the dehumidifier unit. Within the dehumidificationunit are three proportional valves (TCV03, TCV02, and TCV01) thatcontrol the flow of warm and cold water to three heat exchangers 2306,2304, 2200 that are used to heat (TCV03), cool (TCV02), and dehumidify(TCV01). The fans 2202 (SA Flow fans) blow air to the grow room 20, anddampers FC04-FC09 2120 are used to control the air flow to each of thesupply ducting outputs of the line. Return Air is moved across thedehumidification coils to dehumidify the air. In normal operation mode,XC01 2114 and XC03 2118 are closed and XC02 2130 is open and no blendingwith outside air using economization is utilized.

FIG. 22 illustrates a top view of the lighting assembly for a number ofgrow lines of receptacle supports (e.g., towers), according toembodiments of the disclosure. The figure shows five grow lines 202horizontally. According to embodiments of the disclosure, linear arraysof lights are disposed on each side of a grow line 202. According toembodiments of the disclosure, the lights shine down from above thereceptacle supports to illuminate the plants growing out of the sides ofthe receptacle supports. As shown, the lights may be grouped intosections (e.g., sections 2204, 2206).

FIG. 23 illustrates an irrigation subsystem 2300 according toembodiments of the disclosure, including a water supply tank 2302, asupply pump 2304, a return pump 2306, a flow sensor, a supply line 2310,a zone master valve 2312, a lateral, main irrigation line 2314 fromwhich branch irrigation lines 2316 branch off (shown for eight grow roomsections), and a gutter 2318. The main irrigation line 2314 runsparallel to and above the grow line of vertical receptacle supports(e.g., towers). A nozzle at the end of each branch irrigation line 2316allows water to spray down into a funnel disposed at the top of thevertical receptacle support, thus enabling irrigation of the plantssupported by the receptacle support, according to embodiments of thedisclosure. The gutter 2318 includes a gutter water level sensor and asump pump 2320.

In operation, the supply pump 2320 pumps nutrient-enriched water fromthe supply tank 2302 through the supply line 2310 to the branchirrigation lines 2316 via the main irrigation line 2314. The water flowsfrom the nozzles into the receptacle supports. Any water not retained inthe receptacle supports flows into the gutter 2318.

The flow sensor monitors flow rate in the supply line 2310. The supplypump 2304, like many commercial supply pumps, provides an error signalin case of a pump malfunction. In response to an irrigation faultcondition (e.g., the error signal or the flow rate falling below adesired threshold (e.g., 200 liters per minute)), the controller 203executes an irrigation fail safe protocol, as follows according toembodiments of the disclosure: dim the lights (e.g., down to 10% ofstandard illumination) if the irrigation fault condition persists for agiven time period, e.g., 10 minutes; turn off the lights if theirrigation fault condition persists for a further time period, e.g., 30minutes more. According to embodiments of the disclosure, if the faultcondition ends, the controller 203 turns the lights back on.

Flow Sensor

FIG. 24 illustrates a flow sensor element 2502 according to embodimentsof the disclosure. The flow sensor element 2502 includes a digitalthermometer 2504 thermally coupled to a heating element 2506.

FIG. 25A is a simplified block diagram of a digital thermometer 2504,according to embodiments of the disclosure. The digital thermometer 2504may include a temperature sensor 2508, such as a thermistor circuit.Resistance of the thermistor varies with temperature. The thermistorcircuit may include a thermistor in a half-bridge configuration (e.g.,with a resistor divider), so that voltage represents the resistance ofthe thermistor. According to embodiments of the disclosure, the digitalthermometer 2504 includes an analog-to-digital converter (“ADC”) 2509 toconvert the output of the temperature sensor 2508 into a digital value.According to embodiments of the disclosure, logic (not shown) in thedigital thermometer 2504 applies an equation to the output of the ADC todetermine the temperature, according to known techniques. In otherembodiments, the digital thermometer 2504 employs a look-up table 2511to convert the ADC output into a temperature value. For background onmeasuring temperature with a thermistor, please see Application Note1753, A Simple Thermistor Interface to an ADC, 26 Nov. 2002, MAXIMINTEGRATED PRODUCTS, INC., incorporated by reference herein in itsentirety.

FIG. 25B is a block diagram of a DS18B20 programmable 1-WIRE digitalthermometer manufactured by Maxim Integrated Products, Inc. According toembodiments of the disclosure, the digital thermometer 2504 comprisesthe DS18B20 thermometer. The DS18B20 Programmable Resolution 1-WIREDigital Thermometer Datasheet, 19-7487; Rev 6; 7/19, MAXIM INTEGRATEDPRODUCTS, INC., is incorporated by reference herein in its entirety.

Referring back to FIG. 24, the heating element 2506 may comprise anymaterial that experiences ohmic heating, such as a carbon resistor, anichrome wire, a plate (e.g., of dimensions coextensive with, or smallerthan, those of one side of the digital thermometer 2504 packaging), aspiral wrapped around the digital thermometer 2504, or a tube enclosingthe digital thermometer 2504.

According to embodiments of the disclosure, the thermometer 2504 and theheating element 2506 may be thermally coupled by placing them againsteach other and potting them together with a potting compound such asepoxy resin, silicone, or urethane.

FIG. 26 illustrates a flow sensor assembly 2600, according toembodiments of the disclosure. The flow sensor assembly 2600 may beplaced at any location where fluid flows in the controlled agriculturalenvironment of embodiments of the disclosure, including nozzles 1602.According to embodiments of the disclosure, the flow sensor assembly2600 includes digital thermometer 2504 and heating element 2506 of flowsensor element 2502, and a thermally conductive element 2510, which areall thermally coupled to each other. The components may be thermallycoupled together with a potting compound 2512, such as epoxy resin,silicone, or urethane. According to embodiments of the disclosure, thethermally conductive element 2510 may comprise a thermally conductivecup in which the thermometer 2504 and the heating element 2506 reside,or a plate or other shape for thermally coupling the flow sensor element2502 to a fluid 2520 in a fluid channel 2530. The thermally conductivematerial may comprise titanium or stainless steel, for example.

According to embodiments of the disclosure, the thermally conductiveelement 2510 is placed against a flowing fluid 2520 (e.g., nutrientsolution) having a flow rate to be measured. According to embodiments ofthe disclosure, the fluid 2520 may reside in a fluid channel 2530, withthe thermally conductive element 2510 in direct contact with the fluid2520, e.g., via an opening in the fluid channel 2530.

An advantage of flow sensor assembly 2600 over conventional approachesis that no electrical current flows through the thermally conductiveelement 2510. Thus, the thermally conductive element 2510 may employmore fluid-compatible materials than those used for heating element 2506(through which current flows to actively heat heating element 2506),including fluid-compatible materials that are more resistant tocorrosion and erosion than heating element materials (e.g., nichrome)that efficiently generate heat when current is applied. Suchfluid-compatible materials that would be suitable for thermalconduction, but not suitable for heating elements include, for example,titanium, stainless steel, and thermally conductive ceramics. Accordingto embodiments of the disclosure, the thermally conductive element 2510employs materials having the following characteristics: high thermalconductivity (e.g., greater than 5 W/mK), bondability to a polymerenclosure such as a PVC water nozzle or conduit, whereas the heatingelement 2506 employs materials that have a relatively linear resistancetemperature coefficient and resilience to many thermal cycles.

FIG. 27 illustrates a network 2700 of flow sensor assemblies 2600according to embodiments of the disclosure. According to embodiments ofthe disclosure, to determine flow within a fluid channel 2530, a flowsensor assembly 2600 and a second digital thermometer 2702 (e.g., aDS18B20 digital thermometer chip) are thermally coupled to a flowchannel (i.e., fluid channel) 2530 with the flow sensor assembly 2600disposed downstream of the second digital thermometer 2702 with respectto the flow direction. The distance between the flow sensor assembly2600 and the second digital thermometer 2702 may be any length thatenables measurement by the second digital thermometer 2702 of theupstream temperature of the fluid in the channel 2530, e.g., a fewmillimeters. According to embodiments of the disclosure, the flow sensorassembly 2600 and the second digital thermometer 2702 are so smallcompared to the channel 2530 that effectively the entire chip isthermally coupled to the flow channel 2530.

The second digital thermometer 2702 may be separated from the flowingmedium (e.g., nutrient solution, water) by a thermally conductiveelement, such as thermally conductive element 2510 used for flow sensorassembly 2600. The flow sensor assembly 2600 and the second digitalthermometer 2702 provide first and second outputs that representmeasured temperature at their respective locations.

According to embodiments of the disclosure, a microprocessor,microcontroller (e.g., Arduino-compatible) or other logic provides aflow measurement based at least in part upon the first and secondoutputs. The logic may be incorporated into or separate from controller203. The controller may be the same controller 2704 used to control growlights and may itself be responsive to instructions from a higher-level“Farm OS” controller 2706 that controls operations of the entirecontrolled agricultural environment.

The combination of a flow sensor element (thermometer+heater) 2502 andthe second digital thermometer 2702 may be referred to herein as a“differential flow sensor” to distinguished it from the flow sensorelement 2502 itself. In practice, the flow sensor element 2502 and thesecond digital thermometer 2702 of the differential flow sensor may eachbe thermally coupled to the flowing fluid via respective thermallyconductive elements, as described above. The differential flow sensormay be placed at any location in the controlled agricultural environmentof embodiments of the disclosure, including nozzles 1602. A singledifferential flow sensor in combination with a controller or other logicmay be referred to herein as a “flow meter.”

According to embodiments of the disclosure with reference to FIG. 27, toform a sensor network of differential flow sensors, multipledifferential flow sensors may be daisy chained, with the data (DQ) linesof all the flow sensor elements 2502 of the flow sensor assemblies 2600and of all the second digital thermometers 2702 of all the differentialflow sensors tied together. Also, the power lines to all the heatingelements of each integrated flow sensor may be tied together to drawpower from the same source, e.g., constant-current power supply 2708.

Of course, all the differential flow sensors may be grounded to the sameground. Also, if the digital thermometers within the differential flowsensors are not running on parasite power, all the VDD power lines maybe tied together to draw power from the same source. When operating inparasite power mode, the digital thermometer 2504 derives power directlyfrom the data line instead of from an external supply. Power is insteadsupplied using a pullup resistor 2550 on the DQ pin when the bus ishigh. The high bus signal also charges an internal capacitor (C_(PP)),which then supplies power to the device when the bus is low. This methodof deriving power from the single-wire bus is referred to as “parasitepower.”

According to embodiments of the disclosure, the controller 2704communicates with the differential flow sensors over the single dataline (“single wire”). According to embodiments of the disclosure, thecontroller 2704 may communicate commands and data with the differentdifferential flow sensors in a time-multiplexed manner over the dataline, as described in DS18B20, Programmable Resolution 1-Wire DigitalThermometer, Datasheet, Maxim Integrated Products, Inc. 19-7487; Rev 6;7/19 (2019), incorporated by reference herein in its entirety. Thecontroller 2704 may query each differential flow sensor for its measuredtemperature using an address identifying the queried differentialsensor.

According to embodiments of the disclosure, the controller 2704determines the velocity of fluid (flow rate) flowing through the fluidchannel 2530 with a differential flow sensor that generates heat Q,using a convection heat loss equation such as:

Q=hA(T _(heater) −T _(water)).

T_(heater) is the temperature measured by the flow sensor 2502, andT_(water) is the temperature measured by the upstream second digitalthermometer 2702.

A is defined as the heat emitting area of a thermally conductive element2510 that is thermally coupled to the flowing fluid 2520 (e.g., a flatplate, or the area of thermally conductive element 2510 that abutschannel 2530) and h is the coefficient of convection from the equationbelow for the thermally conductive element 2510

${h = \frac{{Nu}*k}{L}}.$

For a nutrient nozzle according to embodiments of the disclosure, flowis determined to be laminar because the Reynolds number (Re) iscalculated to be 180 which is less than the critical transition Reynoldsnumber of 5*10⁵ as found using the equation:

${Re} = \frac{V*x}{\nu}$

where V is the expected maximum velocity of the fluid, x is the traveledlength of the fluid within the nozzle (e.g., length of the nozzle flowchannel) and v is the kinematic viscosity of the fluid. If the maximumexpected velocity of an unclogged nozzle results in laminar flow, thenany lower velocity from a clogged or nozzle will still result in laminarflow and thus the equation for the Reynolds number may be used todetermine velocity of the fluid.

Getting back to the equation for h, for a flat surface like that ofelement 2510 abutting the fluid channel 2530 which contains laminarflow,

${Nu} = {{\frac{h*L}{k}0.644{Re}_{L}^{1/2}} - \Pr^{1/3}}$

where L is the length of the flat surface, k is the thermal conductivityof the fluid, Nu is the Nusselt number, and Pr is the Prandtl number,which is a measure of the relative thickness of the velocity and thermalboundary layer given by the equation:

${{Pr} = \frac{\mu*C_{p}}{k}}.$

In that equation, μ is the dynamic viscosity of the fluid, C_(p) is thespecific heat capacity of the fluid and k was defined earlier. All fluidproperties are evaluated at the “film temperature T_(film)),” which isthe temperature of the fluid adjacent to the thermally conductiveelement 2510, which is

${T_{film} = \frac{T_{heater} + T_{water}}{2}}.$

Putting this all together and solving for the velocity of the fluidgives the equation:

$V = {\frac{v}{x}*\left( \frac{L \times Q}{0.664*\Pr^{1/3}*A*\left( {T_{heater} - T_{water}} \right)} \right)^{2}}$

Based on the fluid velocity (flow rate), the controller 2704 maydetermine whether the flow rate falls below a threshold value thatindicates a blockage in the flow channel. Normal flow rate measured in anozzle above a tower funnel may be, for example, 0.04 liters per second.Thus, the controller may provide an alert of a potential obstruction ata measured rate below the threshold, such as 0.03 liters per second.

Note that, unlike a conventional CTA, in the flow sensor 2502 theheating element 2506 is not part of a Wheatstone bridge circuit. Thelogic (e.g., in the controller 2704) does not perform analog-to-digitalconversion on voltage of a Wheatstone bridge that includes the heatingelement. Moreover, the first digital thermometer 2504 includes atemperature sensor component 2508 that is not actively heated (currentis applied to temperature sensor component 2508 to measure, but not togenerate heat).

Computer System Implementation

FIG. 20 illustrates an example of a computer system 2800 that may beused to execute program code stored in a non-transitory computerreadable medium (e.g., memory) in accordance with embodiments of thedisclosure. The computer system includes an input/output subsystem 2802,which may be used to interface with human users or other computersystems depending upon the application. The I/O subsystem 2802 mayinclude, e.g., a keyboard, mouse, graphical user interface, touchscreen,or other interfaces for input, and, e.g., an LED or other flat screendisplay, or other interfaces for output, including application programinterfaces (APIs). Other elements of embodiments of the disclosure, suchas engine 106, control system 107, and controller 203, may beimplemented with a computer system like that of computer system 2800.

Program code may be stored in non-transitory media such as persistentstorage in secondary memory 2810 or main memory 2808 or both. Mainmemory 2808 may include volatile memory such as random access memory(RAM) or non-volatile memory such as read only memory (ROM), as well asdifferent levels of cache memory for faster access to instructions anddata. Secondary memory may include persistent storage such as solidstate drives, hard disk drives or optical disks. One or more processors2804 reads program code from one or more non-transitory media andexecutes the code to enable the computer system to accomplish themethods performed by the embodiments herein. Those skilled in the artwill understand that the processor(s) may ingest source code, andinterpret or compile the source code into machine code that isunderstandable at the hardware gate level of the processor(s) 2804. Theprocessor(s) 2804 may include graphics processing units (GPUs) forhandling computationally intensive tasks.

The processor(s) 2804 may communicate with external networks via one ormore communications interfaces 2807, such as a network interface card,WiFi transceiver, etc. A bus 2805 communicatively couples the I/Osubsystem 2802, the processor(s) 2804, peripheral devices 2806,communications interfaces 2807, memory 2808, and persistent storage2810. Embodiments of the disclosure are not limited to thisrepresentative architecture. Alternative embodiments may employdifferent arrangements and types of components, e.g., separate buses forinput-output components and memory subsystems.

Those skilled in the art will understand that some or all of theelements of embodiments of the disclosure, and their accompanyingoperations, may be implemented wholly or partially by one or morecomputer systems including one or more processors and one or more memorysystems like those of computer system 2800. In particular, the elementsof automated systems or devices described herein may becomputer-implemented. Some elements and functionality may be implementedlocally and others may be implemented in a distributed fashion over anetwork through different servers, e.g., in client-server fashion, forexample.

Although the disclosure may not expressly disclose that some embodimentsor features described herein may be combined with other embodiments orfeatures described herein, this disclosure should be read to describeany such combinations that would be practicable by one of ordinary skillin the art. Unless otherwise indicated herein, the term “include” shallmean “include, without limitation,” and the term “or” shall meannon-exclusive “or” in the manner of “and/or.”

All references cited herein, including, without limitation, articles,publications, patents, patent publications, and patent applications, areincorporated by reference in their entireties for all purposes, exceptthat any portion of any such reference is not incorporated by referenceherein to the extent it: (1) is inconsistent with embodiments of thedisclosure expressly described herein; (2) limits the scope of anyembodiments described herein; or (3) limits the scope of any terms ofany claims recited herein. Mention of any reference, article,publication, patent, patent publication, or patent application citedherein is not, and should not be taken as an acknowledgment or any formof suggestion that it constitutes valid prior art or forms part of thecommon general knowledge in any country in the world, or that itdiscloses essential matter.

EMBODIMENTS OF THE DISCLOSURE

The following are some exemplary embodiments of the disclosure:

-   1. A digital flow sensor comprising:    -   a flow sensor element comprising a first digital thermometer for        providing a first output and a heating element thermally coupled        to the first digital thermometer.-   2. The flow sensor of embodiment 1, further comprising:    -   a second digital thermometer for providing a second output;    -   logic for providing a flow measurement based at least in part        upon the first and second outputs.-   3. The flow sensor of embodiment 2, wherein the logic is operable to    provide the flow measurement in response to the flow sensor element    and the second digital thermometer being thermally coupled to a    flowing fluid.-   4. The flow sensor of any one of the preceding embodiments, further    comprising a thermally conductive element thermally coupled to the    flow sensor element.-   5. The flow sensor of embodiment 4, wherein the thermally conductive    element is disposed in a wall of a fluid channel to enable thermal    coupling to a flowing fluid in the channel.-   6. The flow sensor of any one of the preceding embodiments starting    with embodiment 4, wherein at least one of the thermally conductive    element or the heating element has a thermal conductivity of at    least 5 W/mK.-   7. The flow sensor of any one of the preceding embodiments, wherein    the flow sensor element includes a single-wire bus for communicating    data and commands.-   8. The flow sensor of any one of the preceding embodiments, wherein    the flow sensor element includes a single-wire bus for communicating    data and commands, and for receiving power.-   9. The flow sensor of any one of the preceding embodiments, wherein    the heating element is not part of a Wheatstone bridge circuit.-   10. The flow sensor of any one of the preceding embodiments, wherein    the logic does not perform analog-to-digital conversion on voltage    of a Wheatstone bridge that includes the heating element.-   11. The flow sensor of any one of the preceding embodiments, wherein    the first digital thermometer includes an integrated temperature    sensor component that is not thermally coupled to a heating element    within the first digital thermometer.-   12. The flow sensor of any one of the preceding embodiments, wherein    the first digital thermometer includes no moving parts.-   13. A flow sensor network comprising a plurality of digital flow    sensors of any one of the preceding embodiments, wherein data lines    of the plurality of digital flow sensors are coupled to the same    network bus for communicating data.-   14. The flow sensor network of embodiment 13, wherein commands are    also communicated over the network bus.-   15. The flow sensor network of any one of the preceding embodiments    starting with embodiment 13, wherein the network bus is a    single-wire bus.-   16. The flow sensor network of any one of the preceding embodiments    starting with claim 13, wherein the heating elements of the    plurality of digital flow sensors are coupled to the same current    source.

What is claimed is:
 1. A digital flow sensor comprising: a flow sensorelement comprising a first digital thermometer for providing a firstoutput; and a heating element thermally coupled to the first digitalthermometer.
 2. The flow sensor of claim 1, further comprising: a seconddigital thermometer for providing a second output; logic for providing aflow measurement based at least in part upon the first and secondoutputs.
 3. The flow sensor of claim 2, wherein the logic is operable toprovide the flow measurement in response to the flow sensor element andthe second digital thermometer being thermally coupled to a flowingfluid.
 4. The flow sensor of claim 1, further comprising a thermallyconductive element thermally coupled to the flow sensor element.
 5. Theflow sensor of claim 4, wherein the thermally conductive element isdisposed in a wall of a fluid channel to enable thermal coupling to aflowing fluid in the channel.
 6. The flow sensor of claim 4, wherein atleast one of the thermally conductive element or the heating element hasa thermal conductivity of at least 5 W/mK.
 7. The flow sensor of claim1, wherein the flow sensor element includes a single-wire bus forcommunicating data and commands.
 8. The flow sensor of claim 1, whereinthe flow sensor element includes a single-wire bus for communicatingdata and commands, and for receiving power.
 9. The flow sensor of claim1, wherein the heating element is not part of a Wheatstone bridgecircuit.
 10. The flow sensor of claim 2, wherein the logic does notperform analog-to-digital conversion on voltage of a Wheatstone bridgethat includes the heating element.
 11. The flow sensor of claim 1,wherein the first digital thermometer includes an integrated temperaturesensor component that is not thermally coupled to a heating elementwithin the first digital thermometer.
 12. The flow sensor of claim 1,wherein the first digital thermometer includes no moving parts.
 13. Aflow sensor network comprising a plurality of digital flow sensors ofclaim 1, wherein data lines of the plurality of digital flow sensors arecoupled to the same network bus for communicating data.
 14. The flowsensor network of claim 13, wherein commands are also communicated overthe network bus.
 15. The flow sensor network of claim 13, wherein thenetwork bus is a single-wire bus.
 16. The flow sensor network of claim13, wherein the heating elements of the plurality of digital flowsensors are coupled to the same current source.
 17. A method of sensingflow comprising: providing a first output from a flow sensor elementcomprising a first digital thermometer; and thermally coupling a heatingelement to the first digital thermometer.
 18. The method of claim 17,further comprising: providing a second output from a second digitalthermometer; and providing a flow measurement based at least in partupon the first and second outputs.
 19. The method of claim 18, whereinproviding the flow measurement comprises providing the flow measurementin response to the flow sensor element and the second digitalthermometer being thermally coupled to a flowing fluid.
 20. The methodof claim 17, further comprising thermally coupling a thermallyconductive element to the flow sensor element.
 21. The method of claim20, further comprising disposing the thermally conductive element in awall of a fluid channel to enable thermal coupling to a flowing fluid inthe channel.
 22. The method of claim 20, wherein at least one of thethermally conductive element or the heating element has a thermalconductivity of at least 5 W/mK.
 23. The method of claim 17, wherein theflow sensor element includes a single-wire bus for communicating dataand commands.
 24. The method of claim 17, wherein the flow sensorelement includes a single-wire bus for communicating data and commands,and for receiving power.
 25. The method of claim 17, wherein the heatingelement is not part of a Wheatstone bridge circuit.
 26. The method ofclaim 18, wherein providing a flow measurement does not compriseperforming analog-to-digital conversion on voltage of a Wheatstonebridge that includes the heating element.
 27. The method of claim 17,wherein the first digital thermometer includes an integrated temperaturesensor component that is not thermally coupled to a heating elementwithin the first digital thermometer.
 28. The method of claim 17,wherein the first digital thermometer includes no moving parts.
 29. Amethod comprising coupling data lines of a plurality of digital flowsensors to a network bus, each digital flow sensor comprising a flowsensor element and a heating element of claim
 17. 30. The method ofclaim 29, wherein the network bus is a single-wire bus.
 31. The methodof claim 29, further comprising coupling the heating elements of theplurality of digital flow sensors to the same current source.